Pacific Underwater Calendar: Killer whales and chinook salmon in July

Back in the summer of 2011, I experienced a life changing moment. With a breathtaking view of Mount Baker in the background, I saw a killer whale eat a salmon. The little girl in me was screaming. I have been in love with killer whales for as long as I can remember. This moment was particularly special for me because I've spent the last few years studying Pacific chinook salmon and killer whale populations off the coast of British Columbia.

Chinook salmon (also known as spring, tyee, or king salmon) are the largest and longest lived species of salmon in B.C., they can weigh over 40 kilograms and spend up to 8 years at sea. The reason I chose chinook salmon for my research was because they are the favourite food of the salmon-loving resident killer whale. There are three types of killer whales in B.C.: residents, transients (now called Bigg's), and offshores.

Offshore killer whales are typically found far from shore in large groups where they hunt for fish and sharks. Bigg's killer whales — named after the late Dr. Michael Bigg the pioneer of killer whale research — feed on marine mammals such as seals, porpoises and whales. Resident killer whales -comprised of a northern and a southern population — are the salmon-eaters. Residents are famous for their social behavior, and are the main attraction for whale watching tours in the province.

Chinook salmon essential to resident populations

Resident killer whales are seriously picky eaters, relying on chinook salmon almost exclusively as their main food source. These resident killer whales feast in July when many different chinook salmon populations return to the rivers where they were born. When killer whales have full bellies, they have more time to socialize, play, and reproduce. For the northern resident killer whale population — this means scratching their salmon-filled bellies along their traditional rubbing beaches. For the southern resident killer whale population — this means jumping out of the water, doing cartwheels, and slapping their tails (see video). When there aren't enough chinook salmon around, resident killer whales spend more time and energy looking for food, and less time socializing.

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Unfortunately, south coast chinook salmon stocks are at extremely low numbers this summer, continuing their downward trend over the last couple years (see Figure 1). Because 70-80% of the resident population's diet comes from chinook salmon, these killer whales have been especially hard hit. Research shows that the mortality rates of resident killer whales increase when chinook salmon numbers are low. Many chinook salmon stocks have declined on the B.C. coast for a variety of reasons, including climate change, habitat destruction, over-fishing, and disease. Depleted chinook salmon populations is the norm in B.C. these days. But it means more than just less social time for killer whales: the long-term survival of resident populations is at risk.

Species at Risk Act

Resident killer whales in B.C. are listed under Canada's Species at Risk Act, meaning the federal government is required to develop a Recovery Plan and an Action Plan to help them. The most severely affected population is the endangered southern resident population, with only 82 individuals (Center for Whale Research), the lowest count in more than 10 years. Although the northern resident killer whale population has recently increased — as well as Bigg's whales — they are still at risk from other factors such as pollution and vessel disturbance.

Figure 1: Fisheries and Oceans Canada (DFO) Lower Fraser River test fishery captures showing the range of Chinook salmon stocks returning to the Fraser River from April-October 2013(red) and the historical averages from 1981-2012(black).

Ensuring there is enough chinook salmon for resident killer whales is a legal requirement. Areas important to the survival of these salmon are legally part of the resident killer whale's critical habitat. Increasing chinook abundance must occur through science-based recovery planning for depleted stocks, and addressing issues such as over-fishing and habitat destruction. Over the longer term, implementation of Canada's Wild Salmon Policy should ensure chinook salmon stocks are both recovered and abundant enough to support killer whales and other species that depend on them.

No simple fix

There is no simple fix for the survival of resident killer whales and Chinook salmon, but every positive step helps. Supporting the creation of a national network of marine protected areas with substantial marine planning so that B.C.'s valuable coastal waters and marine resources are well-managed at an ecosystem level is an important first step.

I feel extremely fortunate to have seen these beautiful animals in the wild. When I imagine an ideal day on the B.C. Pacific coast during the month of July, I picture a well-fed resident killer whale sharing chinook salmon with her calf, while others jump and play in front of a coastal backdrop of green cedars, blue seas, and white capped mountains. I hope that sharing these moments will help others feel inspired to protect the ocean environment for generations to come.

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2 Comments

Jul 26, 201312:29 PM

James Middleton says...

The oceans of Canada’s west coast are among the most productive marine environments in the world and by refusing to greatly increase Marine Protected Areas our Government is failing not only the salmon and whales, but all present and future Canadians. Let us set an example for the rest of the world instead of embarrassing ourselves.

Aug 09, 2013 7:29 PM

Juntae Lee says...

Killer whales are dying due to decrease in number of salmon. The number of salmon is shrinking due to pollution of rivers. To prevent the pollution of river bodies, more strict environmental laws are needed to be enforced. Governments and environmental NGOs have to keep their eyes on industrial activities, so that hazardous wastes wont be dumped into rivers.

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